A centrifugal pump usually includes a motor which drives an impeller to rotate to create a negative pressure inside the pump, such that liquid is continuously drawn in and propelled out. The impeller is an indispensable component of the pump, and its design and construction directly affects the fluid delivery efficiency of the pump.
In a conventional centrifugal pump, the impeller is mounted within a hollow chamber of the volute housing. A large gap usually exists between the impeller and an end wall of the hollow chamber adjacent an inlet. After the fluid enters the hollow chamber via the inlet and is rotated by the impeller, part of the fluid may flow back into the inlet via the gap, which may cause unstable flow velocity of the fluid and hence poor fluid delivery efficiency of the pump.